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450 TWh is the estimated yearly potential of electric power that can be produced from tidal energy. In addition to this comes a large and not yet estimated potential in river flows.

Tidal stream generators are very similar to wind turbines except their below the water surface instead of above or on land. The turbine and generator converts the movement of water coming from change in tide, the kinetic energy, into electricity. Water is 830 times denser than air and therefore can generate electricity at lower speeds than wind turbines.

The device is an advanced solar cell, no bigger than a typical playing card, which is left floating in a pool of water. Then, much like a natural leaf, it uses sunlight to split the water into its two core components, oxygen and hydrogen, which are stored in a fuel cell to be used when producing electricity.

The World Energy Council has estimated that approximately 2 terawatts (2 million megawatts), about double current world electricity production, could be produced from the oceans via wave power.

Wave energy is generally considered to be the most concentrated and least variable form of renewable energy. It is the high power density of wave energy that suggests it has the capacity to become the lowest cost renewable energy source.

Wave energy is a renewable, zero emission source of power

Because wave energy needs only 1/200 the land area of wind and requires no access roads, infrastructure costs are less;

Hartlepool-based JDR Cable Systems is constructing the armored 25- kilometer subsea cable that will connect Wave Hub to the grid and the hub structure that will sit on the seabed. Work also is progressing on the hub assembly, which will provide a connection between the main cable from the shore and the tails leading to the wave energy devices.

Bio fuels are a viable alternative to fossil fuels.

Some examples are that of biodiesel, which entails growing crops that contain high amounts of natural oil then through a process of hydrogenation or refining a more compatible bio diesel, substitute is created.

These are examples of first generation biofuels and due to their nature they may or may not be long-term economically or environmentally viable.

Fuel cell systems are not yet as durable as internal combustion engines, especially in some temperature and humidity ranges.

FCVs are currently more expensive than conventional vehicles and hybrids. Manufacturers must bring down production costs, especially the costs of the fuel cell stack and hydrogen storage, to compete with conventional technologies.

There are over 180,000 fueling stations nationwide. About 40% of those service petroleum diesel fuel, and less than 1% service biodiesel.

Biodiesel is simple to use and requires no costly engine conversions or infrastructure changes to the current delivery system of diesel fuel.

Biofuels

We are working to produce biofuels that are low cost, low carbon, sustainable and able to fulfil the world’s transportation fuel needs on a large scale without compromising food production

Sailboats and sailing ships have been using wind power for thousands of years, and architects have used wind-driven natural ventilation in buildings since similarly ancient times. The use of wind to provide mechanical power came somewhat later in antiquity. The windwheel of the Greek engineer Heron of Alexandria in the 1st century AD is the earliest known instance of using a wind-driven wheel to power a machine.[15][16].

Wind power generates electricity with... No air emissions No fuel to mine, transport, or store No cooling water No water pollution No wastes

Wind power can reduce pollution generated by fossil fuels such as coal, oil, and gas. A typical (750 kW) wind turbine provides enough power for 328 typical (non-electric heating) homes.

A dam-like structure is constructed across an estuary to trap a high tide of water and then let it pass through turbines to generate electricity. The water flow can generate electricity on the falling tide only, or on the falling and rising tide.

but if everyone had cars like ours, there'd be no need for roads."

This ultimately reduces the cost these power plants can sell their electricity

Earth is composed mainly of bodies of water---about 71 percent of the earth's surface is water. Ninety-seven percent of that is found in the oceans. Because the earth's surface is curved, the sun heats it unevenly. This causes winds to blow across the water and generate waves. The sun and moon also exert their gravitational pull on the earth, triggering wave-producing tides. Wave motion energy can be harnessed and generated into electricity.

At 250 kilowatts, the fuel cell produces 40-50% of the electricity for the Environmental Science Center. Its electricity production alone is 47% effective, and the addition of heat recovery allows for up to 60% efficiency

While designed to run on pure hydrogen, Yale’s fuel cell is actually powered by natural gas, 80% of which is usable hydrogen. The fuel cell takes in natural gas and water and produces water, electricity, and hot air.

Cons:

The purchase and set-up of wind turbines can be expensive

Wind turbines require certain constant speeds to be productive (13 mph for large turbines, 9 mph for small turbines)

But as much as it poses a health risk, a group of researchers from the National Renewable Energy Laboratory point out that the relative risks are still light when compared to the use of fossil fuels

Wave energy is generally affected by three main factors: Wind speed - higher wind speed means more wave energy, because the energy is transfered from the wind to the wave. Fetch - the distance of open water over which the wave has travelled across makes a big differenece on wave height and wave energy, as a longer fetch gives the waves longer to 'grow'. Wind duration - with a longer storm, the waves will be bigger.